Is Breast Milk Allergy a Myth?
Published Date:September 24, 2025
By Ali Weatherford
There has been some information circulating in social media recently that might need to be updated and clarified. It’s about foods that you eat that might cause reactions in your baby when you’re breastfeeding. It’s true that your baby can be allergic or intolerant to certain things that get into your breast milk, but there’s some confusion out there about what it looks like, how much it takes, what to do about it, and how the food you eat will have an impact on your baby.
FIRST, babies are not allergic to breastmilk! But…
It is possible to have a reaction to something through breast milk.
It has been shown that the proteins from some of the most allergenic/reactive foods that you eat do get into breast milk. The most common of these are:
- Cow’s milk
- Egg
- Peanut
- Wheat
- Soy
When someone has a food allergy or sensitivity, it’s a reaction to the protein. There are certain foods that are more likely to cause reactions. There are a lot of factors that can lead a particular protein to be a culprit. Food proteins have to survive being processed and cooked, make it through what happens in the digestive system, and then interact with the immune system. Most food proteins just don’t make it that far and so, rarely cause problems for people.
When you’re breastfeeding, there’s an additional step of getting from your body into your breast milk supply and then into your baby. That’s why the list of potential allergens is pretty short and reactions are unusual. But it can happen.
Some good news is that it’s still pretty rare, and that when it does happen it’s very rarely a life threatening kind of reaction. That’s because so little of it gets into your breast milk, that it’s not enough to elicit the worst kind of allergic response. So even if your baby does have a sensitivity or allergy, it might not look like the most severe case. Sometimes it gets dismissed or overlooked because of this. But it definitely happens, and it’s important to listen to your intuition and get it figured out if your baby is having symptoms.
What a Food Intolerance or Allergy Looks Like in a Breastfed Infant
While you won’t be likely to see extreme airway restriction, hives, diarrhea or a drop in blood pressure like in severe reactions, you might notice some other things like:
- Excessive spitting up
- Reflux
- Fussiness
- Not enough dirty diapers
- Blood-streaked stools
- Chronic congestion
- Excessive mucus in stool
- Eczema
- Rashes
These symptoms can lead to other secondary issues like refusing to eat, trouble sleeping, and issues with weight gain.
What You Can Do About It
If you suspect that your baby isn’t tolerating something you’re eating, I would definitely recommend getting some guidance from your pediatrician, IBCLC, or registered dietician. Not all providers have a lot of experience with this, so if someone isn’t helpful, you might find another professional to support you. A lot of times, a parent’s intuition is right on, so if you are continuing to have problems, and your gut is telling you there is something wrong, keep trying to find the support you need.
You can also do some basic things yourself. Just know that it might take some time and patience before you can get the problem solved.
- Elimination diet – A lot of people like to start here. It can be really helpful to have some professional guidance with this, but you can also do this on your own. You might start by eliminating the most common allergen from your diet first, or you might consider the symptoms your baby is having. If your baby is having digestive problems like spitting up and maybe even blood in the stool, starting with dairy might be a good idea since it’s most often associated with those symptoms. When you completely eliminate that food from your diet, it will stop entering your breast milk.
- Clearing the protein from your milk supply – This is where there is a lot of misinformation. Even the food proteins that take the longest to clear are gone within 24 hours, and some are gone by 8 hours. Your milk will no longer contain the problem protein after that as long as you don’t eat anymore of it. So, you might not even have to stop breastfeeding while you’re waiting for your baby’s symptoms to clear.
- Resolving symptoms – What can take longer is for your baby’s body to clear the protein and stop reacting. It might even take a couple of weeks for symptoms to completely clear up. That’s why it can be hard to know for sure what works and what doesn’t when you’re doing an elimination diet. BUT, your baby should definitely be improving more each day once the problem protein is gone from your milk supply. It’s possible that the baby’s symptoms go away much quicker, it just depends on the symptoms and the severity of the allergy or intolerance. It takes some patience.
What Happens As the Baby Grows?
It can be very hard to know how long your baby will be sensitive to a particular food protein. Sometimes, it’s a problem that you see just during infancy and then it goes away. Other times it doesn’t go away at all or the problem develops later.
Using my daughter’s intolerance as an example, after researching for this article, I thought back and can now see that she likely reacted to dairy when I was breastfeeding. I loved all things dairy and ate plenty of it. She spit up A LOT. It was pretty extreme actually, but I was told by her doctor that it was normal. She was gaining weight and was mostly happy. She also had some rashes and strange skin issues that continued for several months. Again, I was told they were normal newborn things and maybe they were. HOWEVER, as a kid, my daughter tended to avoid dairy products. She would never drink a glass of milk, and often refused ice cream. She said they made her belly hurt or feel “too full”. She could eat some cheese without much consequence, and since her reactions were relatively mild and sort of inconsistent, I didn’t think to eliminate it completely. As an older teenager now, she recognizes very clearly that she wants to avoid eating a lot of dairy products, and is learning the limits. Cheeses that are low in lactose like mozzarella don’t bother her much at all in moderation. If she eats very small amounts of other dairy products, she’s able to digest and tolerate it without consequence. But if she has more than a certain amount, she’ll feel really bad. Together, we’ve been learning a lot more about lactose intolerance, and now it all makes sense in hindsight. It can be hard to know how things will end up, but it can definitely improve, or you can find solutions.
As parents, we sometimes just have to learn as we go. We will definitely make some mistakes, but we keep learning and keep trying. It’s so important to reach out for help, and it’s also necessary to trust yourself. You know your child best, and you will probably be able to tell when there is something wrong. There are just some things that don’t have clear answers medically. It might take some effort to find the solutions, but you can definitely have hope that things will get better.
References:
What makes a food protein an allergen? – PubMed
Infant Allergic Reactions to Food Proteins in Human Milk – IABLE
IgE-Mediated Food Allergy | Clinical Reviews in Allergy & Immunology
